1. Field of the Invention
The present invention relates to the field of rolling equipment.
The present invention will namely find a particularly advantageous application in the field of wheelchairs for people having limited physical mobility.
However, the invention can also be used in other areas than wheelchairs.
The invention relates more particularly to an omnidirectional wheel aimed at being mounted namely on a wheelchair in order to permit a mobility thereof in all directions.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
A traditional wheel comprises, on the one hand, at its center a hub, which permits to ensure the guiding in rotation of the wheel relative to its support, such as a frame or an arm, and, on the other hand, at the periphery a rim on which is fixed a tread or a tire, which acts as a rolling surface.
The rotation of a wheel permits a mobility thereof, which is easy in a direction that is perpendicular to the axis of rotation of the wheel. However, a displacement of the wheel in a direction parallel to the axis of rotation is not practical, because of the frictions of the ground on the rolling surface of the wheel.
Wheelchairs require more particularly the presence of multidirectional wheels, which permit a smooth multidirectional mobility, so as to facilitate the displacements for the user of said chair.
Thus, in the state of the art are already known wheelchairs having a plurality of casters having an axis of rotation perpendicular to the axis of rotation of the wheel, whereby said casters can namely be mounted at the level of the circumference of the wheel. This system permits a lateral displacement of the wheel, thanks to the casters, thus reducing the frictions on the tread surface of the wheel.
Such a system has however drawbacks. In particular, the wheels associated with casters have a high complexity and, therefore, difficulties in assembling and an expensive manufacture. On the other hand, in order to permit a regular and smooth rolling, the casters must be mounted at least two-by-two. Another drawback of the use of the casters resides in that they lack flexibility in their tread and they are not suitable for a displacement of the wheelchair on uneven ground; thus, the user of said chair is limited in his displacements to roads having only little roughness.
Some patent documents also evoke the placing of sleeves arranged at the level of the circumference of the wheel, said sleeves forming a regular tread that should permit a displacement of the front wheel backwards and laterally, without any constraint due to frictions on the ground.
For example, the use of sleeves is disclosed in the American patent US 2008/018167. However, the sleeves as mentioned in this document have inevitably a compression at the level of their portion located proximate the wheel rim. This makes the rotation of the sleeve and, hence, the lateral displacement of the wheelchair more difficult. Such a system is thus not optimal for solving the problem of a multidirectional displacement of a wheelchair.
The same applies in the patent NL 1 015 676, which discloses a wheel for skates with casters of the “roller” type including a plurality of rollers, the latter being mounted so that a contact pressure is exerted between two adjacent rollers, resulting into a braking of the rotation of said rollers.
In this document, the side surfaces of the rollers insert against each other under pressure, so that each of the rollers is compressed. This results into a resistance against rotation, said resistance being used to brake the roller skate.
From EP 0556 401 is also known a wheel for a wheelchair including a plurality of auxiliary wheels. The auxiliary wheels include a shaft between two bearings comprising an inclined stop permitting to maintain the auxiliary wheels radially, the bearings being connected to the hub of the main wheel.
This system has the advantage of avoiding the compression constraints existing in the other devices of the prior art.
However, maintaining the wheel by means of only the bearings does not permit an optimal rigidity and strength of the system. In addition, the rotation of the auxiliary wheels about their respective shafts can also be subjected to friction constraints, which inevitably leads to difficulties in the lateral displacement of the wheel and, hence, a fortiori of the wheelchair.